This application claims priority to Japanese Patent Application Number 2010-168667 filed Jul. 27, 2010 in Japan, the entire disclosure of which is incorporated by reference herein in its entirety.
1. Technical Field
The present invention relates to a light-emitting element, a display device, and an electronic apparatus.
2. Related Art
There have been proposed display devices in which in producing organic electroluminescence elements (so-called organic EL elements), a red light-emitting layer and a green light-emitting layer provided in organic EL elements which emit lights of respective colors are formed by a coating method, and a blue light-emitting layer is formed by a vacuum deposition method (evaporation method) (refer to, for example, Japanese Unexamined Patent Application Publication No. 2007-73532).
This technique focuses attention on the point that red light- and green light-emitting organic EL elements formed by a coating method such as an ink jet method have practical levels of emission life (luminance life) and luminous efficiency (current efficiency or external quantum efficiency), but a blue light-emitting organic EL element formed by a coating method often has an emission life and luminous efficiency below practical levels, while a blue light-emitting organic EL element formed by a vacuum deposition method often has an emission life of several times or more as long as that of the blue light-emitting organic EL element formed by the coating method and thus has a practical level of emission life. That is, even when the emission life and luminous efficiency of a color light-emitting organic EL element formed by a liquid-phase process such as an ink jet method are below practical levels, the same color light-emitting organic EL element formed by a vapor-phase process such as a vacuum deposition method may have practical levels of emission life and luminous efficiency.
In such a display device, a red organic EL element (red pixel) and a green organic EL element (green pixel) have a configuration in which a blue light-emitting layer is formed by a vacuum deposition method on a red light-emitting layer and a green light-emitting layer possessed by the respective organic EL elements. That is, the blue light-emitting layer is formed over the entire surface including the red light-emitting layer and the green light-emitting layer by the vacuum deposition method. Therefore, a method for producing a display device having a such configuration is optimum for producing a display device including a large panel because of no need for depositing the blue light-emitting layer selectively only in a blue organic EL element (blue pixel) using a high-definition mask.
However, in this case, since the blue light-emitting layer is provided in contact with the red light-emitting layer and the green light-emitting layer in the red organic EL element and the green organic EL element, respectively, electrons are often not sufficiently injected to the red light-emitting layer and the green light-emitting layer from the blue light-emitting layer.
Therefore, in the red organic EL element (red pixel) and the green organic EL element (green pixel), light may be undesirably emitted from the blue light-emitting layer, thereby decreasing color purities of read and green colors.
Namely, in a light-emitting element including a plurality of layers (light-emitting function layers) having the function of emitting light which are provided between a cathode and an anode, there is a problem that light cannot be selectively or dominantly emitted from a desired layer among the layers having the function of emitting light.